The present invention relates to an elevation and index apparatus of a water hydraulic driven type and, more particularly, to an elevation and index apparatus of a water hydraulic driven type having a high level of cleanliness and washability as well as high positioning accuracy and a high responsiveness. The elevation and index apparatus of a water hydraulic driven type is particularly useful for food processing machines.
(Related Art)
Hitherto, as an index table of a machine tool, there has been used an elevation and index mechanism having an elevation table and a rotary table. The elevation table has a piston disposed so as to move upwardly or downwardly by a cylinder mechanism while restricting its rotary movement about its axis. The rotary table is supported on the elevation table so as to pivot about the axis.
Relating to a mechanism for positioning a rotary table by driving and rotating the table held rotatably through a gear reduction mechanism by a servo-motor, proposed was a mechanism which can reduce a positioning error resulting from a backlash of the gears by using a mechanism biasing the table in either rotary direction at the positioning period after driving the rotary table.
A roller gear cam mechanism has been known for long time, and is sold as a single part, for example, under the trade name xe2x80x9cINDEX DRIVExe2x80x9d.
On the other hand, a so-called water hydraulic component has been developed from the point of view of cleanliness, safety, saving resources and the other purposes, which uses clean water, in place of oil that has been used as a working medium for conventional oil hydraulic components. The water hydraulic component is basically the same as the conventional oil hydraulic component using oil as the working medium, in that the water hydraulic component using water as the working medium utilizes the pressure of a fluid. Therefore, the former is almost the same as the latter in terms of operation principles and structural configuration. Since water has problems in that its lubricating properties are lower than oil and it is prone to cause rust, structures and materials are devised for the water hydraulic components using water as the working medium so as to overcome these problems.
In the current food processing industry, a large number of works are conducted manually because of the fact that objects to be processed, such as meat, agricultural products, etc. vary substantially in size, shape, etc. depending on individuals. Automation of the food processing has strongly been demanded because reducing manual work is more effective and useful from the point of view of prevention of contamination with bacteria such as Escherichia coli, etc., saving of labor, and for other reasons.
For such machines for use in automation of processing food, an accurate positioning of objects to be processed is demanded to adjust the individual differences of the processed objects, in order to improve the quality and yield of the products by the automated processing of the objects on the basis of measurements for shapes of the individual objects and results of the measurements. In particular, a so-called base machine by which the objects to be processed by a food processor are measured and transferred to the processing location is required to satisfy many requirements from the point of view of productivity, such as high-speed processing ability, improved speed, compactness, etc., in addition to an accurate positioning performance. Moreover, as machines for processing fob are required to allow its food-processing section to be washed by spraying water under high pressure, the base machine is also required to have high resistance to washing.
As devices for driving and controlling the base machine, there have hitherto been extensively used components that can be driven electrically or hydraulically. However, considering a washing by high-pressure water for electrically driven components, in order to prevent danger of electric leakage of failures due to water penetration into electric components such as a cylinder or a motor (hereinafter referred to as xe2x80x9can actuatorxe2x80x9d) for generating a large power, it is required to enclose the periphery of the actuator so as to seal it against water penetration. Therefore, enclosing of the electrical components may result in a larger size of the entire system, or require air purging in accordance with the sealing conditions and, additional accessory instruments are occasionally needed.
Moreover, the enclosing of the electrical devices may cause problems due to poor heat radiation or dissolving of the grease caused by heating up of the actuators. Further, it may require a connecting mechanism in order to extract an output through the sealed portion, or it may result in a decrease in output. On the other hand, the oil hydraulic components have the lesser risk of causing failures due to washing of the apparatus, and can even realize a higher output and responsiveness than the electrically drivable devices. However, if standard materials are used for the hydraulic components, there is a risk that rust is produced due to exposure to washing water, or that the surroundings are contaminated with oil that is leaked from the inside of the components. Furthermore, oil available for use with food processing machines can be used as operating oil for the components; however, such oil cannot be said to be thoroughly non-toxic and non-hazardous to the environment and the human body.
In addition, there may also be used a pneumatically driven component that is recognized as a clean drive system, although it is little used for a base machine. Such a pneumatic driven component; however, may suffer from difficulties in that a high power cannot be produced as compared to that produced by using hydraulic driven components and electric driven components. Also, it is anticipated that it is difficult to achieve desired high positioning accuracy due to the lack of rigidity resulting from compressibility of air. Furthermore, a problem might result from discharging of lubricant oil from the components, and the compressor for generating air pressure, in the form of oil mist. Given those problems, a pneumatic driven component is not suitable for use in food processing machines.
In order to solve the problems prevailing in the conventional food processing devices, extensive studies have been made regarding elevation and index apparatuses for use particularly with a base machine of a food-processing machine. As a result of extensive studies, it was found that an elevation and index apparatus of a water hydraulic driven type having a particular compact structural configuration could achieve desired machine performance.
Therefore, the present invention has the object to provide an elevation and index apparatus of a water hydraulic driven type having a compact structural configuration as well as a high level of cleanliness, washability, responsiveness, output and positioning accuracy, which can be used in a transfer-load section that is used as a base machine particularly for a food processing machine.
In order to achieve the object, the present invention provides an elevation and index apparatus for loading an object to be processed, and transferring and locating the loaded processing object by moving upwardly or downwardly and indexing the loaded processing object. The elevation and index apparatus is of a water hydraulic driven type consisting of a rotary table supported pivotally by a bearing, a power transmission mechanism composed of a follower node fixed to the rotary table and a drive node engaged with the follower node, a motor that has an output shaft thereof connected to the power transmission mechanism and that is fixed to a table base supporting the bearing, a cylinder disposed so as to move linearly along the pivotal center of the follower node fixed to the table base, a main elevation shaft extending through a communicating bore formed in the center of the rotary table connected to an output shaft of the cylinder, an elevation and index table connected to the rotary table connected to the main elevation shaft through a bearing so as to move upwardly or downwardly while restricting its pivotal movement, and a casing disposed outside the table base and enclosing the power transmission mechanism, wherein the motor and the cylinder are each of a water hydraulic driven type, and the motor and the cylinder are each controlled by a hydraulic control valve.
With the configuration as described above, the elevation and index apparatus of a water hydraulic driven type according to the present invention can be a compact mechanism with larger elevating and lowering strokes, as compared with an elevation and index apparatus of a configuration with a rotary table disposed on an elevation table. This is so because, the communicating bore is formed in the center of the rotary table and the main elevation shaft extends entirely through the communicating bore to support the elevation and index table disposed over the rotary table. Furthermore, the driving of the rotary table is controlled by the water hydraulic cylinder and motor as well as the water hydraulic control valve, so that there is no risk that the surroundings are polluted and short circuiting results due to leakage of a driving medium.
Moreover, because a water hydraulic actuator is made of a rustproof material, it is not necessary to take into account failures to be caused by water and rust, and to make the configuration of the component protective from washing water. Therefore, the use of water hydraulic components can provide a higher freedom of configuration for the apparatus, thereby readily producing a compact apparatus. In addition, as the water hydraulic actuator is driven by liquid pressure, like the oil hydraulic actuator, it can realize output and responsiveness as high as the oil hydraulic actuator.
Furthermore, the apparatus according to the present invention has the casing disposed so as to enclose the power transmission mechanism, so that the mechanism portion requiring lubrication is not sprayed directly with washing water, thereby improving speed and reliability of the apparatus. In addition, even if water would somewhat penetrate into the inside of the casing, the enclosed mechanism is composed mainly of simple mechanical parts so that the occurrence of significant failures and the shortening of a life time of the device can be prevented.
According to another aspect of the present invention, the elevation and index apparatus of a water hydraulic driven type is preferably provided with a biasing mechanism that is disposed so as to rotate the rotary table in either direction with a force somewhat smaller than the driving force of the motor by using a reduction gear mechanism as the power transmission mechanism, when the rotary table is located in the vicinity of a predetermined indexing position.
When the reduction gear mechanism composed of a combination of gears is used as the power transmission mechanism in the above manner, the apparatus driven by the reduction device can be made smaller in size and the capacity of the driving motor can be reduced. Further, the elevation and index table can be positioned to desired accuracy even if the motor is positioned with comparably lower accuracy. In this instance, even if a water hydraulic motor, for example, would be positioned at a predetermined position, the elevation and index table may be caused to deviate to a slight extent by a working reaction force due to a backlash of the gears, or an error would be caused to occur in the positioning of the is elevation and index table due to such a backlash. Providing the rotary table with a biasing force and rotating the rotary table slightly by means of the biasing force, however, can control impacts of the backlash.
According to a further aspect of the present invention, the elevation and index apparatus of a water hydraulic driven type is preferably provided with a water hydraulic driven motor integrated with a reduction device of a water lubrication type and a built-in sensor, and a water hydraulic cylinder with a built-in sensor.
A sensor has the risk that it causes failures due to contact with washing water permeating into the device, or to a physical force such as impact, etc. upon spraying with washing water. In this embodiment, the sensor is built in the water hydraulic motor and the water hydraulic cylinder, so that the sensor does not undergo the impact resulting from the direct spraying of washing water. Therefore, the apparatus according to the present invention can reduce the occasions of causing failures due to the washing of the motor and the cylinder, thereby achieving improvements in the reliability of the power transmission mechanism as a whole.
According to a still further aspect, the present invention is preferably directed to the elevation and index apparatus of a water hydraulic driven type having a rotary position sensor installed inside the casing, which senses the rotary position of the rotary table.
With this configuration of the apparatus, an absolute position of the rotary table can be detected, which is needed for the alignment with a processing tool, and an actual position of the rotary table can be detected without undergoing the influences of a backlash resulting from the reduction mechanism. In this configuration, it is preferred that a sensor for use in detecting the position of the table is disposed inside the casing because this configuration does not require the sensor to be protected by special waterproof treatment procedures.
According to a still further aspect, the present invention is preferably directed to the elevation and index apparatus of a water hydraulic driven type having a control unit that is so adapted as to-control the motor following a target pass pre-computed on the basis of a sensor signal from the sensor built in the motor at the point of time of starting the positioning of the rotary table, and then shifted to control the motor on the basis of a signal from the rotary position sensor at the point of time when the target pass reaches a target position.
A sensor having high precision is required if the motor is controlled only by the sensor mounted on the rotary table side. However, as in the still further embodiment of the present invention, wherein the two sensors are to be shifted so as to comply with the conditions, the motor can be controlled with high accuracy even if the sensors are not so high in precision.
Further, according to another aspect, the elevation and index apparatus of a water hydraulic driven type is preferably provided with the power transmission mechanism consisting of a combination of a concave globoidal cam with a roller cam follower.
The use of a combination of the concave globoidal cam with the roller cam follower as the power transmission mechanism can realize a high indexing accuracy even if the positioning accuracy of the motor is lower than the case where the reduction gear mechanism is used as the power transmission mechanism and the biasing mechanism is used in the manner as described above. This configuration rarely causes a backlash; however, it entails the loss of space to some extent.
According to a still further aspect, the present invention is preferably directed to the elevation and index apparatus of a water hydraulic driven type which uses a water hydraulic driven motor integral with a reduction device of a water lubrication type as the motor, and a water hydraulic driven cylinder with a built-in mechanism decelerating at the terminal end of the stroke is used as the cylinder.
By using a water hydraulic motor with the reduction device built therein, since positioning accuracy of the motor can be a low level that does not require a sensor with high precision, and the cylinder can be operated simply to abut with the terminal end, it is possible to obtain a desirable level of accuracy by a simple ON-OFF operation of the water hydraulic control valve.
The other objects, features and advantages of the present invention will become apparent in the course of the following description with reference to the accompanying drawings.